,Test Bank – Chapter 1: Adaptation by Natural Selection
(Theme: Darwin’s theory of natural selection, adaptation, fitness, and how
traits spread in populations)
1.
Which condition is necessary for natural selection to operate within a
population?
A. Individuals must acquire traits during their lifetime.
B. There must be heritable variation among individuals.
C. Every individual must reproduce equally.
D. Evolution must occur through genetic drift alone.
✅ Correct Answer: B
Rationale: Natural selection requires heritable variation in traits so that
differential reproductive success can shape the population over generations.
Acquired traits (A) are not inherited, equal reproduction (C) would prevent
selection, and drift (D) is random rather than adaptive.
2.
How does Darwin’s concept of “fitness” differ from the everyday use of the
term?
A. It refers to physical strength only.
B. It measures the probability of survival to old age.
C. It refers to reproductive success relative to others.
D. It measures genetic stability within populations.
✅ Correct Answer: C
Rationale: In evolutionary biology, fitness is defined as relative
reproductive success — the number of viable offspring compared to others.
,Strength (A) and longevity (B) do not guarantee passing genes on. Genetic
stability (D) may influence inheritance but is not the measure of fitness.
3.
What best explains why antibiotic resistance spreads rapidly in bacterial
populations?
A. Random chance increases resistant bacteria equally across all populations.
B. Resistance genes are inherited and confer survival advantage under
antibiotics.
C. All bacteria mutate at the same rate when exposed to antibiotics.
D. Resistant bacteria reproduce less often than non-resistant strains.
✅ Correct Answer: B
Rationale: Resistant bacteria survive and reproduce more successfully in
environments with antibiotics, spreading the trait through natural selection.
Random drift (A) is insufficient, equal mutation rates (C) do not explain
frequency changes, and lower reproduction (D) would decrease resistance.
4.
Why is variation within a population considered the raw material for natural
selection?
A. Without variation, mutations cannot occur.
B. Variation ensures some individuals have higher reproductive success
under changing environments.
C. Populations without variation evolve faster.
D. Variation eliminates the effects of genetic drift.
✅ Correct Answer: B
Rationale: Variation allows differential survival and reproduction. If the
environment changes, individuals with advantageous traits can increase in
,frequency. Mutations (A) still occur regardless, (C) is false since no variation
slows adaptation, and (D) is incorrect because drift still acts on variation.
5.
Which of the following is an example of directional selection?
A. Human birth weight stabilizing around 3–3.5 kg.
B. Darker moths increasing in frequency during the Industrial Revolution.
C. Maintenance of sickle-cell allele due to malaria resistance.
D. Equal preference for intermediate beak sizes in finches.
✅ Correct Answer: B
Rationale: Directional selection favors one extreme of a trait distribution —
like darker moths gaining survival advantage in polluted environments. Birth
weight (A) is stabilizing, sickle-cell (C) is balancing, and intermediate beaks
(D) is also stabilizing selection.
6.
What does Darwin mean by “descent with modification”?
A. Organisms gradually become more complex over time.
B. Species change through generations by natural selection.
C. Individuals modify themselves during life and pass it on.
D. Only extinct species show evolutionary modification.
✅ Correct Answer: B
Rationale: “Descent with modification” refers to populations changing
over generations as traits are inherited and modified. Evolution is not always
toward complexity (A), acquired changes (C) are Lamarckian, and (D)
incorrectly restricts modification to extinct species.
,7.
If a mutation increases the likelihood of producing more offspring, what term
best describes its evolutionary consequence?
A. Genetic drift
B. Increased fitness
C. Neutral variation
D. Artificial selection
✅ Correct Answer: B
Rationale: A mutation that boosts reproduction increases fitness, making it
more likely to spread by natural selection. Drift (A) is random, neutral
variation (C) has no reproductive effect, and artificial selection (D) requires
human intervention.
8.
Why is natural selection often described as a non-random process?
A. It produces traits specifically needed by the species.
B. It consistently favors traits that improve survival and reproduction.
C. It eliminates mutations from a population.
D. It guarantees progress toward perfection.
✅ Correct Answer: B
Rationale: Natural selection is non-random because traits that confer
higher fitness are more likely to persist, unlike random drift. It does not
“design” traits (A), remove all mutations (C), or guarantee perfection (D).
9.
What role does heritability play in adaptation?
, A. It determines whether advantageous traits can be passed to offspring.
B. It ensures all individuals in a population are identical.
C. It prevents mutations from accumulating in populations.
D. It guarantees survival of the fittest individuals.
✅ Correct Answer: A
Rationale: For adaptation to occur, traits must be heritable so natural
selection can act across generations. Populations are not identical (B),
mutations accumulate regardless (C), and survival is probabilistic, not
guaranteed (D).
10.
How does stabilizing selection affect a population’s trait distribution?
A. It increases extremes at both ends.
B. It favors intermediate traits, reducing variation.
C. It promotes new mutations in the population.
D. It causes random changes unrelated to environment.
✅ Correct Answer: B
Rationale: Stabilizing selection favors intermediate phenotypes,
maintaining average values and reducing extremes (e.g., human birth weight).
Increasing extremes (A) describes disruptive selection, (C) is unrelated, and
(D) is genetic drift.
11.
Which process explains why male peacocks have elaborate tails despite
higher predation risk?
A. Natural selection for survival
B. Genetic drift acting randomly
C. Sexual selection favoring traits that increase mating success
D. Artificial selection by humans
(Theme: Darwin’s theory of natural selection, adaptation, fitness, and how
traits spread in populations)
1.
Which condition is necessary for natural selection to operate within a
population?
A. Individuals must acquire traits during their lifetime.
B. There must be heritable variation among individuals.
C. Every individual must reproduce equally.
D. Evolution must occur through genetic drift alone.
✅ Correct Answer: B
Rationale: Natural selection requires heritable variation in traits so that
differential reproductive success can shape the population over generations.
Acquired traits (A) are not inherited, equal reproduction (C) would prevent
selection, and drift (D) is random rather than adaptive.
2.
How does Darwin’s concept of “fitness” differ from the everyday use of the
term?
A. It refers to physical strength only.
B. It measures the probability of survival to old age.
C. It refers to reproductive success relative to others.
D. It measures genetic stability within populations.
✅ Correct Answer: C
Rationale: In evolutionary biology, fitness is defined as relative
reproductive success — the number of viable offspring compared to others.
,Strength (A) and longevity (B) do not guarantee passing genes on. Genetic
stability (D) may influence inheritance but is not the measure of fitness.
3.
What best explains why antibiotic resistance spreads rapidly in bacterial
populations?
A. Random chance increases resistant bacteria equally across all populations.
B. Resistance genes are inherited and confer survival advantage under
antibiotics.
C. All bacteria mutate at the same rate when exposed to antibiotics.
D. Resistant bacteria reproduce less often than non-resistant strains.
✅ Correct Answer: B
Rationale: Resistant bacteria survive and reproduce more successfully in
environments with antibiotics, spreading the trait through natural selection.
Random drift (A) is insufficient, equal mutation rates (C) do not explain
frequency changes, and lower reproduction (D) would decrease resistance.
4.
Why is variation within a population considered the raw material for natural
selection?
A. Without variation, mutations cannot occur.
B. Variation ensures some individuals have higher reproductive success
under changing environments.
C. Populations without variation evolve faster.
D. Variation eliminates the effects of genetic drift.
✅ Correct Answer: B
Rationale: Variation allows differential survival and reproduction. If the
environment changes, individuals with advantageous traits can increase in
,frequency. Mutations (A) still occur regardless, (C) is false since no variation
slows adaptation, and (D) is incorrect because drift still acts on variation.
5.
Which of the following is an example of directional selection?
A. Human birth weight stabilizing around 3–3.5 kg.
B. Darker moths increasing in frequency during the Industrial Revolution.
C. Maintenance of sickle-cell allele due to malaria resistance.
D. Equal preference for intermediate beak sizes in finches.
✅ Correct Answer: B
Rationale: Directional selection favors one extreme of a trait distribution —
like darker moths gaining survival advantage in polluted environments. Birth
weight (A) is stabilizing, sickle-cell (C) is balancing, and intermediate beaks
(D) is also stabilizing selection.
6.
What does Darwin mean by “descent with modification”?
A. Organisms gradually become more complex over time.
B. Species change through generations by natural selection.
C. Individuals modify themselves during life and pass it on.
D. Only extinct species show evolutionary modification.
✅ Correct Answer: B
Rationale: “Descent with modification” refers to populations changing
over generations as traits are inherited and modified. Evolution is not always
toward complexity (A), acquired changes (C) are Lamarckian, and (D)
incorrectly restricts modification to extinct species.
,7.
If a mutation increases the likelihood of producing more offspring, what term
best describes its evolutionary consequence?
A. Genetic drift
B. Increased fitness
C. Neutral variation
D. Artificial selection
✅ Correct Answer: B
Rationale: A mutation that boosts reproduction increases fitness, making it
more likely to spread by natural selection. Drift (A) is random, neutral
variation (C) has no reproductive effect, and artificial selection (D) requires
human intervention.
8.
Why is natural selection often described as a non-random process?
A. It produces traits specifically needed by the species.
B. It consistently favors traits that improve survival and reproduction.
C. It eliminates mutations from a population.
D. It guarantees progress toward perfection.
✅ Correct Answer: B
Rationale: Natural selection is non-random because traits that confer
higher fitness are more likely to persist, unlike random drift. It does not
“design” traits (A), remove all mutations (C), or guarantee perfection (D).
9.
What role does heritability play in adaptation?
, A. It determines whether advantageous traits can be passed to offspring.
B. It ensures all individuals in a population are identical.
C. It prevents mutations from accumulating in populations.
D. It guarantees survival of the fittest individuals.
✅ Correct Answer: A
Rationale: For adaptation to occur, traits must be heritable so natural
selection can act across generations. Populations are not identical (B),
mutations accumulate regardless (C), and survival is probabilistic, not
guaranteed (D).
10.
How does stabilizing selection affect a population’s trait distribution?
A. It increases extremes at both ends.
B. It favors intermediate traits, reducing variation.
C. It promotes new mutations in the population.
D. It causes random changes unrelated to environment.
✅ Correct Answer: B
Rationale: Stabilizing selection favors intermediate phenotypes,
maintaining average values and reducing extremes (e.g., human birth weight).
Increasing extremes (A) describes disruptive selection, (C) is unrelated, and
(D) is genetic drift.
11.
Which process explains why male peacocks have elaborate tails despite
higher predation risk?
A. Natural selection for survival
B. Genetic drift acting randomly
C. Sexual selection favoring traits that increase mating success
D. Artificial selection by humans
